snd_mix.c

quakeIII源码这个不用我多说吧

					
					merge1 = vec_mulo(sampleData1,volume_vec);
					merge1 = vec_sra(merge1,volume_shift);					

					d2 = vec_add(merge0,d2);
					d3 = vec_add(merge1,d3);

					/* Store destination sample data */
					*(vector signed int *)&samp[i] = d0;
					*(vector signed int *)&samp[i+2] = d1;
					*(vector signed int *)&samp[i+4] = d2;
					*(vector signed int *)&samp[i+6] = d3;

					i += 8;
					vectorCount--;
					s0 = s1;
					sampleOffset += 8;
				}
				if (sampleOffset == SND_CHUNK_SIZE) {
					chunk = chunk->next;
					samples = chunk->sndChunk;
					sampleOffset = 0;
				}
			}
		}
#else			
		for ( i=0 ; i<count ; i++ ) {
			data  = samples[sampleOffset++];
			samp[i].left += (data * leftvol)>>8;
			samp[i].right += (data * rightvol)>>8;

			if (sampleOffset == SND_CHUNK_SIZE) {
				chunk = chunk->next;
				samples = chunk->sndChunk;
				sampleOffset = 0;
			}
		}
#endif
	} else {
		fleftvol = ch->leftvol*snd_vol;
		frightvol = ch->rightvol*snd_vol;

		ooff = sampleOffset;
		samples = chunk->sndChunk;
		



		for ( i=0 ; i<count ; i++ ) {

			aoff = ooff;
			ooff = ooff + ch->dopplerScale;
			boff = ooff;
			fdata = 0;
			for (j=aoff; j<boff; j++) {
				if (j == SND_CHUNK_SIZE) {
					chunk = chunk->next;
					if (!chunk) {
						chunk = sc->soundData;
					}
					samples = chunk->sndChunk;
					ooff -= SND_CHUNK_SIZE;
				}
				fdata  += samples[j&(SND_CHUNK_SIZE-1)];
			}
			fdiv = 256 * (boff-aoff);
			samp[i].left += (fdata * fleftvol)/fdiv;
			samp[i].right += (fdata * frightvol)/fdiv;
		}
	}
}

void S_PaintChannelFromWavelet( channel_t *ch, sfx_t *sc, int count, int sampleOffset, int bufferOffset ) {
	int						data;
	int						leftvol, rightvol;
	int						i;
	portable_samplepair_t	*samp;
	sndBuffer				*chunk;
	short					*samples;

	leftvol = ch->leftvol*snd_vol;
	rightvol = ch->rightvol*snd_vol;

	i = 0;
	samp = &paintbuffer[ bufferOffset ];
	chunk = sc->soundData;
	while (sampleOffset>=(SND_CHUNK_SIZE_FLOAT*4)) {
		chunk = chunk->next;
		sampleOffset -= (SND_CHUNK_SIZE_FLOAT*4);
		i++;
	}

	if (i!=sfxScratchIndex || sfxScratchPointer != sc) {
		S_AdpcmGetSamples( chunk, sfxScratchBuffer );
		sfxScratchIndex = i;
		sfxScratchPointer = sc;
	}

	samples = sfxScratchBuffer;

	for ( i=0 ; i<count ; i++ ) {
		data  = samples[sampleOffset++];
		samp[i].left += (data * leftvol)>>8;
		samp[i].right += (data * rightvol)>>8;

		if (sampleOffset == SND_CHUNK_SIZE*2) {
			chunk = chunk->next;
			decodeWavelet(chunk, sfxScratchBuffer);
			sfxScratchIndex++;
			sampleOffset = 0;
		}
	}
}

void S_PaintChannelFromADPCM( channel_t *ch, sfx_t *sc, int count, int sampleOffset, int bufferOffset ) {
	int						data;
	int						leftvol, rightvol;
	int						i;
	portable_samplepair_t	*samp;
	sndBuffer				*chunk;
	short					*samples;

	leftvol = ch->leftvol*snd_vol;
	rightvol = ch->rightvol*snd_vol;

	i = 0;
	samp = &paintbuffer[ bufferOffset ];
	chunk = sc->soundData;

	if (ch->doppler) {
		sampleOffset = sampleOffset*ch->oldDopplerScale;
	}

	while (sampleOffset>=(SND_CHUNK_SIZE*4)) {
		chunk = chunk->next;
		sampleOffset -= (SND_CHUNK_SIZE*4);
		i++;
	}

	if (i!=sfxScratchIndex || sfxScratchPointer != sc) {
		S_AdpcmGetSamples( chunk, sfxScratchBuffer );
		sfxScratchIndex = i;
		sfxScratchPointer = sc;
	}

	samples = sfxScratchBuffer;

	for ( i=0 ; i<count ; i++ ) {
		data  = samples[sampleOffset++];
		samp[i].left += (data * leftvol)>>8;
		samp[i].right += (data * rightvol)>>8;

		if (sampleOffset == SND_CHUNK_SIZE*4) {
			chunk = chunk->next;
			S_AdpcmGetSamples( chunk, sfxScratchBuffer);
			sampleOffset = 0;
			sfxScratchIndex++;
		}
	}
}

void S_PaintChannelFromMuLaw( channel_t *ch, sfx_t *sc, int count, int sampleOffset, int bufferOffset ) {
	int						data;
	int						leftvol, rightvol;
	int						i;
	portable_samplepair_t	*samp;
	sndBuffer				*chunk;
	byte					*samples;
	float					ooff;

	leftvol = ch->leftvol*snd_vol;
	rightvol = ch->rightvol*snd_vol;

	samp = &paintbuffer[ bufferOffset ];
	chunk = sc->soundData;
	while (sampleOffset>=(SND_CHUNK_SIZE*2)) {
		chunk = chunk->next;
		sampleOffset -= (SND_CHUNK_SIZE*2);
		if (!chunk) {
			chunk = sc->soundData;
		}
	}

	if (!ch->doppler) {
		samples = (byte *)chunk->sndChunk + sampleOffset;
		for ( i=0 ; i<count ; i++ ) {
			data  = mulawToShort[*samples];
			samp[i].left += (data * leftvol)>>8;
			samp[i].right += (data * rightvol)>>8;
			samples++;
			if (samples == (byte *)chunk->sndChunk+(SND_CHUNK_SIZE*2)) {
				chunk = chunk->next;
				samples = (byte *)chunk->sndChunk;
			}
		}
	} else {
		ooff = sampleOffset;
		samples = (byte *)chunk->sndChunk;
		for ( i=0 ; i<count ; i++ ) {
			data  = mulawToShort[samples[(int)(ooff)]];
			ooff = ooff + ch->dopplerScale;
			samp[i].left += (data * leftvol)>>8;
			samp[i].right += (data * rightvol)>>8;
			if (ooff >= SND_CHUNK_SIZE*2) {
				chunk = chunk->next;
				if (!chunk) {
					chunk = sc->soundData;
				}
				samples = (byte *)chunk->sndChunk;
				ooff = 0.0;
			}
		}
	}
}

/*
===================
S_PaintChannels
===================
*/
void S_PaintChannels( int endtime ) {
	int 	i;
	int 	end;
	channel_t *ch;
	sfx_t	*sc;
	int		ltime, count;
	int		sampleOffset;


	snd_vol = s_volume->value*255;

//Com_Printf ("%i to %i\n", s_paintedtime, endtime);
	while ( s_paintedtime < endtime ) {
		// if paintbuffer is smaller than DMA buffer
		// we may need to fill it multiple times
		end = endtime;
		if ( endtime - s_paintedtime > PAINTBUFFER_SIZE ) {
			end = s_paintedtime + PAINTBUFFER_SIZE;
		}

		// clear the paint buffer to either music or zeros
		if ( s_rawend < s_paintedtime ) {
			if ( s_rawend ) {
				//Com_DPrintf ("background sound underrun\n");
			}
			Com_Memset(paintbuffer, 0, (end - s_paintedtime) * sizeof(portable_samplepair_t));
		} else {
			// copy from the streaming sound source
			int		s;
			int		stop;

			stop = (end < s_rawend) ? end : s_rawend;

			for ( i = s_paintedtime ; i < stop ; i++ ) {
				s = i&(MAX_RAW_SAMPLES-1);
				paintbuffer[i-s_paintedtime] = s_rawsamples[s];
			}
//		if (i != end)
//			Com_Printf ("partial stream\n");
//		else
//			Com_Printf ("full stream\n");
			for ( ; i < end ; i++ ) {
				paintbuffer[i-s_paintedtime].left =
				paintbuffer[i-s_paintedtime].right = 0;
			}
		}

		// paint in the channels.
		ch = s_channels;
		for ( i = 0; i < MAX_CHANNELS ; i++, ch++ ) {		
			if ( !ch->thesfx || (ch->leftvol<0.25 && ch->rightvol<0.25 )) {
				continue;
			}

			ltime = s_paintedtime;
			sc = ch->thesfx;

			sampleOffset = ltime - ch->startSample;
			count = end - ltime;
			if ( sampleOffset + count > sc->soundLength ) {
				count = sc->soundLength - sampleOffset;
			}

			if ( count > 0 ) {	
				if( sc->soundCompressionMethod == 1) {
					S_PaintChannelFromADPCM		(ch, sc, count, sampleOffset, ltime - s_paintedtime);
				} else if( sc->soundCompressionMethod == 2) {
					S_PaintChannelFromWavelet	(ch, sc, count, sampleOffset, ltime - s_paintedtime);
				} else if( sc->soundCompressionMethod == 3) {
					S_PaintChannelFromMuLaw	(ch, sc, count, sampleOffset, ltime - s_paintedtime);
				} else {
					S_PaintChannelFrom16		(ch, sc, count, sampleOffset, ltime - s_paintedtime);
				}
			}
		}

		// paint in the looped channels.
		ch = loop_channels;
		for ( i = 0; i < numLoopChannels ; i++, ch++ ) {		
			if ( !ch->thesfx || (!ch->leftvol && !ch->rightvol )) {
				continue;
			}

			ltime = s_paintedtime;
			sc = ch->thesfx;

			if (sc->soundData==NULL || sc->soundLength==0) {
				continue;
			}
			// we might have to make two passes if it
			// is a looping sound effect and the end of
			// the sample is hit
			do {
				sampleOffset = (ltime % sc->soundLength);

				count = end - ltime;
				if ( sampleOffset + count > sc->soundLength ) {
					count = sc->soundLength - sampleOffset;
				}

				if ( count > 0 ) {	
					if( sc->soundCompressionMethod == 1) {
						S_PaintChannelFromADPCM		(ch, sc, count, sampleOffset, ltime - s_paintedtime);
					} else if( sc->soundCompressionMethod == 2) {
						S_PaintChannelFromWavelet	(ch, sc, count, sampleOffset, ltime - s_paintedtime);
					} else if( sc->soundCompressionMethod == 3) {
						S_PaintChannelFromMuLaw		(ch, sc, count, sampleOffset, ltime - s_paintedtime);
					} else {
						S_PaintChannelFrom16		(ch, sc, count, sampleOffset, ltime - s_paintedtime);
					}
					ltime += count;
				}
			} while ( ltime < end);
		}

		// transfer out according to DMA format
		S_TransferPaintBuffer( end );
		s_paintedtime = end;
	}
}